Is anybody know how to resolve clean head problem
You should start with cleaning the head, if that doesn’t help, there may be a more serious problem with the head’s condition. You have to enter the service mode and check what the individual tracks look like.
How to enter service mode ?
Press Stop and Play and hold them pressed wen powering on the DCC player.
When do you get the clean head message.
With original pre-recorded tapes or recordable tapes ?
My 730 and 951 will often show this message with recordable tapes but still play and record them perfectly. In my 900 and DD82 and 600 the same tapes have no problems or errors.
It seems to be an message common to the 730/951 series.
If it play’s OK you should not be worried.
Most often its not the head, but the tape.
See Restoring a Digital Compact Cassette and solving your dropouts - YouTube
There is also a post of a 3D printed tool which helps in keeping the cassette open, to clean the felt pad or replace it.